Process for producing dense charcoal



, L.'F.'HAWLEY. mocis's FOR PRODUCING DENSE CHARCOAL.

APPLICATION mm APR.3, 1919.

"Pai snt ed Fb. 22

UNITED STATES PATENT OFFICE.

LEE F. HAWLEY, OF MADISON, WISCONSIN, ASSIGNOR TO THE UNITED STATES OF AMERICA.

PROCESS FOR PROITUCING DENSE CHARCOAL.

Specification of Letters Patent. Patented F b 22 1921.

Application filed April 3, 1919. Serial No. 287,316.

To all whom it may concern:

Be it known that I, LEE F. HAWLEY, a citizen of the United States, residing at Madison, in the county of Dane and State of Wisconsin, have invented certain new and useful Improvements in Processes for Producing Dense Charcoal, of which the following is a specification.

This invention relates to an improved process and apparatus for making a very dense and homogeneous charcoal from wood or similar vegetable material.

Ordinarily, the distillation of wood in the manufacture of charcoal has provided a light porous charcoal. The density of the resultant charcoal has always varied with the type of wood used, a very heavy dense wood providing a charcoal normally more dense than that made from the lighter types of wood. As a result of the present invention it is now possible to obtain from the lighter types of wood a charcoal much more dense than that heretofore obtained from the heaviest woods.

The present invention makes it possible to provide a charcoal having a density of at least .95 when an ordinary light wood is used, and a density of at least 1.05 when this same wood has been given a preliminary hydrolyzing treatment.

The process comprises the comminution of the wood to saw-dust or wood flour and the compression of this material in molds into solid blocks. These blocks are formed under a pressure of at least 30,000 pounds per square inch. The blocks thus formed are then distilled and at the same time subjected to a directly applied mechanical compression involving widely varying pressures as differentiated from constantly applied pressure. By the term varying is meant a pressure increasing from fifty pounds per square inch to one hundred and twenty pounds per square inch and then decreasing through the same range in successive alternations. [t has been found that an unusually dense charcoal is produced when the pressure is increased regularly from fifty to one hundred and twenty pounds followed by a decrease through the same range with regularly recurring cycles of such increasing and decreasing pressure. Such pressure on the briquets during distillation will vary froma minimum of fifty pounds per square inch to a maximum of one hundred and twenty pounds per square inch through regular recurrmg cycles. This remarkable result is effected by the mechanical compression dur- 1ng dlstillation and is due in part to the fact that there is a stage in the distillation of the blocks of compressed wood, just as the wood 1s decomposing into charcoal, when the charcoal is slightly plastic and a sufficiently great pressure therefore closes the pores and interstices thereof and forms a homogeneous dense charcoal. One other reason for the remarkable results obtained is that during'the period of low pressure the vapors generated by distillation are allowed to escape freely from the briquets, whereas during the periods of high compression the pores of the charcoal are closed and the vapors and gases cannot escape.

The detailed steps in the process may carried'out as described hereinafter. ordinary wood, such as birch, maple, or pine is cut or ground to a finely divided condition like saw-dust or wood flour. This comminuted material is then compressed in any suitable mold, not shown, under a pressure of at least fifteen tons, 30,000 pounds, to the square inch, thus forming a solid block of wood having a density of about 1.10. These blocks or briquets are preferably circular in to face in a metal tube, having a diameter slightly greater than that of the briquets. If placed face to face within the tube the briquets form a rod of compressed wood.

However, if it is desired to space the briquets apart, either to permit the passage of gases or to preserve the identity of the briquets, this may be done by introducing between the briquets thin sheets of metal of the same diameter of the briquets, or smaller than the bore of the tube. Endwise pressure is applied to the column of briquets. This pressure is variable and is applied in cycles varying from periods using fifty pounds per square inch to periods using a hundred and twenty pounds persquare inch. The tube and its contents are subjected to a distillation temperature of at least three hundred degrees C. during which treatment the pressure is varied as above described. The plastic stage of the material during distillation covers only a small range of temperatures,

from about 280 C.300 (3., and if the distillation temperature is carried much above this point is not necessary, and often not desirable, to apply extreme pressure during the last stage of distillation.

Volatile products of distillation consisting of tar, pyrohgneous acid and gases can be trapped and used as desired as in the usual distillation of wood.

The same unusual results and dense charcoal may be obtained by utilizing a hydrolyzed wood product as the material for the briquets. In the process using hydrolyzed wood the comminuted wood is treated with dilute acid, "preferably sulfuric acid, and high pressure steam, about 100 pounds per square inch, the water, sugar and other soluble materials are removed, the remaining material dried and briqueted and distilled as before. The resultmg wood products remaining after the extraction process is produced in large and commercial quantities in the manufacturing plants engaged in the manufacture of ethyl alcohol from waste wood. If this residue is briqueted and distilled under the conditions of this invention the resultant charcoal is denser, about 1.05, than that obtained directly from wood by the process.

The process may be conducted in any suitable form of apparatus capable of performing the steps specified. The briquets may be formed in any suitable machine. The combined distillation and variable compression steps re uire an unusual type of apparatus, a suita le form of which is provided for by the present invention, which form is illustrated in the accompanying drawing, in whicl1- Figure 1 is a vertical sectional elevation illustratmg the compression tube mounted in the distilling chamber, 9

Fig. 2 is a sectional view taken line 22 of Fig. 1,

Fig. 3 is a view taken on the line 33 of Fig. 1 looking in the direction of the arrow, and

F 1g. 4 illustrates diagrammatically the arrangement of contacts and circuits for effecting the variable pressure feature.

Referr1ng in detail to the drawing 1 ind cates the masonry of the end walls of a distillation furnace, 2 indicates the side walls and 3 the top of the furnace. necessary strength for the structure is made certain by the liberal use of metal reinforcing where necessary. Each of the end walls has two parallel I-beams 4 positioned vertlcally and mounted in a concrete base 5. Suitable braces 6 are provided to strengthen the lower ends of the beams 4 and tie-rods 7 extend from the upper partof the beams 4 to further brace the structure. The furnace is long and narrow and is adapted to be heated by any type of fuel. As illuson the trated, the furnace is constructed to use gas or oil as fuel. Adjacent the lower part of the side walls 2 and spaced along the sides of the same are a series of ports or openings 8 adapted to receive burner nozzles projecting from any suitable supply gas pipe or oil pipe. The flame and hot gases pass upward and through the outlet openings 9 provided in the top 3.

The apparatus for compressing the briuets during distillation includes a cylinrical metal tube or pipe 10 extending longitudinally of the furnace and projecting beyond the end walls thereof. This pipe 10 is necessarily of heavy metal and in order to conform with the preferred type of briquet should have a 5 inch bore. The pipe 10 is positioned and securely held in one end wall 1 by the facing clamps 11 which are screw threaded on the pipe 10 and which clamp the wall and I- beams. The opposite end of the pipe 100 is securely positioned in the opposite end wall but is not clamped to thewall, thus allowing for longitudinal movement resulting from expansion or contraction of the tube during heating. Briquets are inserted into the bore of the ipe 10 through the end opening 12 which is provided with a cover plate 13 adapted to be bolted in place over the end of the pipe 10. Gases and vapors generated during the distillation pass upward and outwardly through the gas outlet passage 14 which is located between the cover plate 13 and the end of the furnace. Compression is effected by means of a plunger 15 having a drive rod 16 projecting beyond the packing gland 17 and extending to drive means as indicated by the worm drive 18. A motor 19 is provided to operate the worm drive 18 b connection through a chain or belt 20. 'l he mechanism for effecting the variable compression, hereinbefore described, will be understood from the following description. The drive rod 16 is formed in two parts and the adjacent ends are provided with guide lates 16 and 16 having rollers 21 adapte to engage the guide rails 22 which are positioned parallel to the rod 16 and thus adapted to prevent the vertical or lateral bucklingof the ends of the rod 16. The plates 16* and 16 have countersunk seats 23 and 23 adapted to receive the compression spring 24 which latter is designed and 28 and 28 which latter are insulated from each other and from their respective supports 16 and 16". For example, 28 and 28 may be set so that when the pressure on the spring 24 is 120 pounds, 27 touches 28. and when the pressure drops to 50 pounds 27 will be in contact with 28". A contact between 27 and 28 will start the driving motor 19 by energizing asolenoid 29 and thus drawing in rocker arm 30 closing the switch 31 and completing the circuit through the motor 19. A contact between 27 and 28 will energize the solenoid 32 and operate to draw in the rocker arm 30 and open the switch 31 and thus open the motor circuit. By adjusting 28 and 28 it is therefore possible, to obtain any range of pressure desired throughout the distillation.

If 28 and 28 are very close together, a practically constant pressure is maintained, but if 28" and 28 are adjusted some distance apart, thepressure is constantly varying throughoutthe distillation process. It has been found that with pressures varying from 50 pounds to 120 pounds, the uality of the charcoal is very much better tian in the case where the limits of pressure are, for instance only 80 pounds to 100 pounds, which latter variation is substantially just enough to give a satisfactory operation of the makeand-break control mechanism. The movement of the plunger 15 is reciprocatory and is provided for by an interrupted drive rod making it possible to avoid rotary movement of the plunger.

The invention described and claimed in the copending application Serial Number 287,315 provides for a change in the nature of thematerial treated by the use of certain details of the process and certain pressures applied during distillation. The present invention is particularly directed toward the manner of applying variable pressure during distillation.

'What I claim is:

l. The process of making charcoal having a specific gravity of at least .95 from wood which'comprises comminuting wood, forming blocks of the comminuted wood, subjecting the blocks to pressure of. at least 30,000 pounds to the square inch, and dis-.

tilling the blocks under a directly applied v mechanical pressure increasing from 50 poundsper square inch to 120 pounds per square inch and then decreasing through the same range in successive alternations.

2. The process of making a dense and homogeneous charcoal which comprises forming blocks by compressing comminuted wood, subjecting the blocks to a pressure of at least 30,000 pounds per square inch prior to distillation, and subjecting the blocks to a combined distilling temperature and to a directly applied mechanical pressure increasing from 50 pounds per square inch to 120 pounds per square inch and then decreasing through the same range in successive alternations.

3. The process of making charcoal having a specific gravity of at least .95 which comprises forming blocks by compressing comminuted wood, subjecting the blocks to a pressure of at least 30,000 pounds per square inch prior to heating them, subject ing the blocks to a combined heat treatment of 300 C. and to a directly applied mechanical pressure increasing from 50 pounds per square inch to 120 pounds per square inch and then decreasing through thesame range in successive alternations.

4. The process of making charcoal having a specific gravity of at least .95 from wood,

which process comprises comminuting wood,

forming blocks of the comminutedwood, subjecting the blocks to mechanical pressure to compress the same, and distilling the blocks under directly applied mechanical pressure increasing from low pressure to high pressure and then decreasing from high pressure to low pressure in successive alternations.

5. The process of making a dense homogeneous charcoal which process comprises treating blocks of woody material to a com- I bined distilling temperature and to a di- I rectly applied recurrent mechanical pressure always greater than atmospherlc pressure and increasing and decreasing through the same range of pressure in successive alternations.

In testimony whereof I have affixed my signature.

LEE F. HAWLEY. 

